In U.S. Pat. No. 3,308,326 to S. H. Kaplan, there is disclosed a color television picture tube including a viewing screen comprised of three interlaced patterns of target elements. One pattern is red emitting, one pattern is green emitting, and one pattern is blue emitting. In order to improve the image contrast of the screen for viewing in relatively bright ambients, that patent suggests placing a red-transmitting color filter in front of the red-emitting elements, either as a separate layer in front of the red-emitting elements, or as a thin overcoating or layer surrounding each red-emitting phosphor particle. It has been found that practical filter layers which surround the phosphor particles absorb too much of the light emitted from the phosphor particles, with the result that the displayed image is not as bright as it could be.
The novel image display, which may be a color television picture tube, comprises a luminescent viewing screen including a layer of phosphor particles and color filter particles adhered to the surfaces of the phosphor particles and .Iadd.partially .Iaddend.covering .[.between 20 and 80 percent of.]. the surfaces of those phosphor particles. The phosphor particles are emissive of light in a particular portion of the visible spectrum, and the color filter particles are transmissive of light in those portions of the spectrum and absorptive of light in other portions of the visible spectrum. By only partially covering the phosphor particles with filter particles, the transmission, absorption, and reflection of light from different portions of the visible spectrum may be tailored to optimize the brightness and contrast of the displayed image in relatively bright ambients.
The invention may be applied to monocolor and multicolor displays. In multicolor displays, the filter particles may be applied to the phosphor particles in one or more of the constituent color elements of the display. In one form of the invention, the layer of filter-particle-coated phosphor particles may be backed up with a layer of phosphor particles having no filter particle coating thereon.